Boxes of cardboard or other sheet material, which are to be processed in packaging machines, are commonly prepared in a flattened tubular form. They are then folded such that their side surfaces and flaps projecting from these surfaces intended to form the ends of the box lie on one or other of the two planes adjacent to one another. Boxes flattened in this way are arranged in a line in a magazine provided in known feeding devices for the packaging machines. The magazine is defined at the front by a fixed support face and at the rear by a plate which may be moved towards this face; by means of suitable pressure the line of boxes stored is held against support members defining this face. Suction members, disposed between the face and the packaging machine, operate in the machine cycle to extract a flattened box from the support members and, with suitable assistance, unfold and open the box into a tubular, prismatic form and insert it in the machine. To keep the boxes of the magazine constantly adjacent to the support face whilst they are being progressively extracted, they are supported by feed means, in practice of the chain type, which move towards the face in a suitable timed relationship with the packaging machine and are held at the rear by the plate which is detachably connected to the feed means.
Obviously the supply device must be filled with new boxes at certain intervals. The re-supplying operation usually involves an additional line of boxes being disposed behind the plate, in a space of the magazine defined between the main plate and a secondary rear plate, as a result of which there is formed a detachable connection with the feed means of the supply device. Consequently, by manual operation, the main plate is either detached from the feed means or removed from the position in which it faces and contacts the boxes. The secondary plate, after being suitably connected to the said means, replaces the main plate and acts on either the new or the old boxes. The main plate is then manually retracted and, immediately in front of the secondary plate, is caused to return to the position in which it faces and contacts the boxes and is connected to the feed means. The secondary plate is finally detached from these means, this plate being retracted to form the said space again.
During the operation for re-supplying the boxes, it is difficult to ensure the maintenance of the pressure required for the efficient removal of the boxes by the suction means. Moreover, the various operations require particular skills and are exacting and difficult particularly if carried out by a single employee.